Tons of false positive errors reported

I just installed the beta build (2162).  I was previously using the latest stable version (5.1.3?).  I immediately notice that I get a bunch of errors and warnings for things that are perfectly valid.  Upon first glance it looks like these issues only occur when using objects that are in referenced assemblies (not projects in the solution).  For example, referencing log4net.dll and calling LogManager.GetLogger(typeof(MyClass)) produces an ambiguous invocation error.  The GetLogger method is overloaded and you can provide either a string or a Type object so my usage is perfectly valid.  I also have another library that I reference and objects that I get from its API causes a "Local variable 'xyz' is never used" warning even though I am using it (oddly, the quick fix option offers to move to outer scope rather than just remove the variable).  This behavior seems very much broken.  Am I doing something wrong here?  Do I need to delete my ReSharper settings or something?  It is completely unusable in this state.